About 200 species: mainly in North and South America, widely naturalized elsewhere; five species (four introduced) in China.

Alternantherapurpurea Y. T. Chang & M. J. Lai (Landscape Architecture [Taipei] [1] (4): 125. 1990, not Pynaert, 1879) was described from Taiwan. We have seen no specimens of this taxon and are therefore unable to treat it in this account. Further revisionary study is necessary.